Drive shaft noise

The bike is a 1982 XJ650J. While riding recently my passenger mentioned hearing a "clack-clack" noise under her as I cornered. I couldn't hear anything when I listened to it so I continued to ride it without a passenger.

I was climbing a hill on the highway when there was a loud noise like the bottom of the engine was hit by a rock thrown up by the front wheel, yet I hadn't seen a rock or felt the tire go over one. I immediately pulled over and investigated. I'm not sure if that noise was anything to do with the problem, or if I actually did kick a rock up with the tire.

With the bike on the center stand I put it in gear. In the higher gears there was a definite clacking noise coming from the drive shaft area, but with the noise of the engine and exhaust leaks it was difficult to trace the exact source.

I trailered the bike home and tried to find the source of the noise. The bike worked fine in all gears but the noise was still there if I put my ear to a screwdriver and listened to the drive shaft housing. It appeared to be loudest near the weld before the housing bolts onto the final drive.

The wheel can rotate an inch or more when the bike is in gear with the engine off, so I began to suspect the u-joint. I also thought perhaps the u-joint was causing the drive shaft to be out of balance and causing the noise I'd heard, so I removed the swing arm assembly and the drive shaft etc.

I found the u-joint appears quite new and I can't feel any play in it when manipulating it by hand. However if I put the drive shaft on it there is a bit of play in the spline shaft where they connect. If I hold the U-joint in one hand right over the splines so that the moving parts of the joint aren't in use, and the drive shaft in the other hand, there is a bit of movement as I turn the drive shaft while turning the other hand in the opposite direction. It's not a huge amount of movement but I suspect this is supposed to have no play.

At the other end of the shaft the oil seal that slides into the final drive housing appears to be a bit damaged, and I recall finding what looked like water contamination in the final drive earlier this season. That was all flushed out several times and hadn't showed any further contamination, but I have not been riding in the rain much at all.

I held the portion of the gear on the rear drive that the drive shaft mates with, and turned it back and forth to check for play. It makes a noticable noise when reversing direction and has some play in it. I see in the manual that "gear lash" is supposed to be measured here, which I'm unfamiliar with. Is that term referring to the play I'm feeling here?

Any ideas on what I need to do to get this bike back on the road?

 

My understanding of your problem is:
You have play in the shaft spline and the u-joint cage. This is bad, replace it.
You have nasty sounds and signs of damage on the rear input seal coupled with water intrusion in the rear gear. This is also bad. I would make the assumption that the rear end is going to dump on you before too long and the "rock" you didn't hit might have been a broken tooth passing through the crown gear. I would replace the rear assembly ASAP. You can find the complete rear off these bikes on Flea-bay for about $50.
My 2 cents.

 

Thanks Robert.

 

I had a similiar issue as of recently and it did turn out to be in the final drive. I got a replacement off ebay and problem solved. My 2 cents.

 

Did you tear your old assembly apart by any chance? I've not seen the innards of one of these units and am curious as to how difficult it would be to pull one apart. One also wonders if the parts are still available.

 

It might be just a U-Joint.

Either way; you'll be checking everything mentioned above on your way in.

If you want to "Peek" ...
Grab the Rubber Boot at the back of the engine and lift it away.
Push it to the rear as far as it can go.
Look in there and you see the Universal Joint.
(It's the four-ended bearing connecting the Drive Shaft to the Engine Output Shaft)
Put the bike in gear.
Have somebody rotate the Rear Wheel back and forth a few inches.
If that U-Joint has ANY Play in it ... its dead.
If you can ... reach-in and hold the Engine Shaft still and "Feel" for play.
There should be NO Play in the U-Joint.

 

In my particular situation, it was a clicking noise whenever the clutch was engaged. I took a look at my U-joint, nothing to show there. When I put in the new rear end, the problem ceased. I am not sure exactly what the issue was, but obviously something in the rear end. With 46,000+, I'm not complaining!!

 

Well I pulled the rear end off and took it and the drive shaft and u-joint to the dealer. He felt there was not enough movement in any of them to warrant replacement. Any movement I had felt he described as normal gear lash. I did find the swing arm bearings needed changing and will be doing that tomorrow.

After posting this thread I found myself having to do an unexpected move for health reasons (mold in walls) so I've been unable to spend any time or money on the bike. I'll put it back together tomorrow and see how it feels.

I still have concerns that perhaps a tooth broke off a gear somewhere in the gear box or final drive, but haven't been able to dig into it. I picked up some more fluid for the final drive so I can drain it before riding and check for any metal in the nearly new fluid in the unit.

I'd like to pull the cover off the main gearbox/tranny and check for any obvious damage, but I don't have a new gasket for the cover. I do have some silicone gasket making goop. Will this work ok to seal it back up?

 

Why don't you see if you can "Feel" it before you go "Looking" for it!

Remove the Plugs and Jack-over the Engine by hand.
Go four revolutions in each gear.
Test the mesh as you go through the four complete revolutions by reversing the motion.
Clockwise from 12 -to- 3 ... 3 -to- 12 ... 3 -to- 6 ... 6 -to 3 ... and so on.
Until you have gone four complete revolutions in all the gears.

If you have a broken gear ... you will feel it.
If you feel it in only one ratio ... that will tell you its a tranny gear.
If you feel it in all the ratios ... that will indicate its in the Middles.

It's extraordinarily difficult to break the Middle Gears. A panic application of the brakes while in motion is likely to do damage to a transmission gear or the Clutch Boss Gear before the Middle Gear is harmed.

It would be far less labor intensive to visually inspect the Clutch Boss Gear and Shaft Gear through the Clutch and replace the Clutch Boss before pulling the engine and splitting the Cases to find out you didn't need to remove the engine and do a great deal of unnecessary work to fix what has broken.

Drain the Oil and Probe the Sump with a Flex-shaft Magnet. You might get a clue as to what too look for if the Magnet retrieves a fragment of the gear.

 

Great advice Rick, thanks!

 

I'd check the ball bearings in the rear end that support the shaft as it enters the final drive. You might have a collapsed bearing cage in there, allowing the balls to move around, which would then allow the shaft to move sideways a bit as clearance opened up in the bearing where there wasn't a ball to support the inner race anymore.

There's an off chance that the sprag clutch in the middle gear has loosened up somehow, but that's a far rarer occurrence I would think.